In a conventional cyclone separator a gas supply pipe has a horizontal section that opens into the horizontal inlet spiral of the cyclone. Operational experience with such a cyclone has shown that material deposits frequently occur in the horizontal section of the gas supply pipe which joins the inlet spiral of the cyclone, and these deposits greatly restrict the flow of gas. These disruptions are particularly serious in cyclones which are intended for use with hot gases charged with fine material. For example, in cases where the cyclone is the lowest stage of a multi-stage cyclone heat exchanger serving to preheat the fine material, the gas supply pipe is formed by the exhaust gas pipe from a rotary kiln which is connected downstream from the cyclone heat exchanger and serves for final burning of the preheated fine material, and the gas supply pipe which serves as a calciner is provided with an arrangement for supplying additional fuel.
The temperatures of the gas and the material at the inlet to the cyclone encourage particles of material to stick to the relatively cooler walls of the gas supply pipe or of the cyclone. When low-grade fuels are used in the gas supply pipe which serves as a calciner this disadvantageous effect is aggravated because a proportion of these fuels burns out in the cyclone or in the part of the gas supply pipe which opens into the inlet spiral of the cyclone. The material deposits formed during overheating can become so firmly set that they can hardly be removed by conventional means.
The conditions in that part of the gas supply pipe which joins the horizontal inlet spiral of the cyclone and also runs horizontally are particularly unfavorable when the preceding section of the gas supply pipe runs vertically downwards from above. In this case the centrifugal forces coming into effect when the particles of material are deflected from the vertical to the horizontal cause an increased deposit of particles of material in the horizontal part of the gas supply pipe.
The object of the invention, therefore, is to construct a cyclone of the type referred to in such a way that these disadvantages are avoided and disruptive material deposits are prevented from forming in that part of the gas supply pipe which joins the horizontal inlet spiral of the cyclone.